1. Field of the Invention
The present invention is in the field of medical instruments. More specifically, it relates to an apparatus for delivery and collection of gases to and from a patient used during anesthesia.
2. Description of Related Art
Delivery of gases and monitoring of the patient's airway (capnography) is necessary during sedation anesthesia or analgesic anesthesia. Currently, for the majority of monitored anesthetic care (MAC), conscious sedation, standby, or any other procedure that involves the administration of sedative agents or anesthetics, nasal cannula are used as a method of supplemental oxygen delivery to the patient. The cannula are inserted into the nares, where the outflow of oxygen is inhaled by the patient, through the nose. This increases the margin of safety for oxygen delivery because the majority of sedatives are associated with a decrease in respiratory drive and can cause short or prolonged periods of apnea. In addition to sedatives that alter respiration activity, certain types of trauma and illnesses will also decrease the respiratory drive.
Many anesthesiologists have attempted to modify the design of the oxygen cannula, to not only deliver oxygen, but to also detect carbon dioxide, by inserting a variety of devices from angiocatheters to intravenous extension tubing to aid the sampling of carbon dioxide directly into the capnographic equipment. In one instance, an extra port in the nasal cannula was added in an attempt to improve carbon dioxide detection.
However, these devices work in a limited manner. They do not detect carbon dioxide sufficiently when the flow of oxygen is high. They also do not allow the sampling port (mouthpiece) to obtain an adequate amount of CO.sub.2 for detection. The sampling port is under continuous suction; should it come against a structure or septum, it easily occludes or kinks. Additionally, not all patients breath through their nose; thus, negligible amounts of carbon dioxide would be detected if sampling at the level of the nares.
In U.S. Pat. No. 4,821,736, issued to Watson on Apr. 18, 1989, entitled, "HEAD-MOUNTED DEVICE FOR SUPPORTING BREATHING CIRCUIT TUBES AND SENSOR," a device for positioning the carbon dioxide sensor and breathing tubes adjacent the centerline of the forehead and above the head is taught. This system includes as its principal elements, in serial arrangement, an endotracheal tube, a sensor, a pair of breathing circuit tubes, and a breathing machine. The distal end of the endotracheal tube has a portion which is inserted in one of the patient's nostrils. The supporting device requires a cushion, a rigid plate, a headband, and two mushroom connecting members. The cushion is positioned lengthwise across the forehead with an inner surface placed on the forehead and on opposing outer surfaces. Central to this invention, the sensor and tubes are held securely along the patient's forehead without pulling on or otherwise irritating any part of the patient.
U.S. Pat. No. 5,046,491, issued to Derrick on Sep. 10, 1991, entitled, "APPARATUS AND METHOD FOR RESPIRED GAS COLLECTION AND ANALYSIS," teaches a nasal gas cannula and an oral gas capture member constructed and arranged to avoid or minimize contact with the patient's mouth and other facial surfaces. This patent emphasizes maintaining a substantially fluid tight seal between a mask and surfaces of the patient's face. Central to this invention is an oral gas hood (mask) with an approximate ellipsoidal peripheral configuration with a major axis and a minor axis, each of which is respectively larger than the length and height of the patient's mouth.
U.S. Pat. No. 5,636,630, issued to Miller, et al., on Jun. 10, 1997, entitled, "RESPIRATORY DEVICE AND METHOD THEREFOR," teaches of a conduit passing above the patient's left and right ears, coupled to the patient's nostrils for supplying a fluid to the patient, a coupling portion contacting a back portion of the patient's head, and a cavity through which the conduit portion passes for securely coupling the conduit portion around the patient's head. The coupling means is located below the patient's left and right ears, on the backside of the patient's head. Unlike the other cited prior art, Miller's invention is restricted to only one conduit line, presumably for detection or delivery of gas, but not both.
Watson, Derrick, and Miller all use head-mounted devices. However, they do not utilize a flexible lever or arm rotatably attached to a headset, for positioning the conduit tubular members close to the patient's orifices. In Watson, a headband is necessary to secure the conduit tubes to the patient's forehead. Similarly, in Derrick, an oral gas hood is secured to the patient's skin about the mouth and nose, with conduit tubing traversing about and around the patient's head. Additionally, the mounting of the conduit assembly in a headset fashion has not been suggested or disclosed in any of the cited prior art. Furthermore, in other gas detection and delivery designs, the nosepiece is intrusively mounted to the nasal passages and then expanded in order to create a compression fit that precludes air leakage.
The problems of occluding, kinking, maintaining a seal about the patient's orifices for continuous suction, and detecting carbon dioxide when the flow of oxygen is high, remain in various prior art designs.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an apparatus and method for mounting the mouthpiece of an oxygen delivery and carbon dioxide detection system nonintrusively to the patient's orifices.
It is another object of the present invention to provide an apparatus for attaching conduit tubes close to, but not touching, the patient's orifices.
A further object of the invention is to provide an apparatus and method for delivering oxygen and detecting carbon dioxide in a respiratory device that is not prone to occlude or kink.
It is yet another object of the present invention to provide an apparatus and method for gas delivery, detection, and monitoring that does not decrease the respiratory drive during operation.
A further object of the present invention is to provide an apparatus and method for gas delivery, detection, and monitoring that is adjustable for attachment on either side of the patient while providing minimum contact with the patient.
Still other advantages of the invention will in part be obvious and will in part be apparent from the specification.